US20060016176A1 - Diesel exhaust aftertreatment device regeneration system - Google Patents

Abstract

A diesel exhaust aftertreatment device regeneration system includes an exhaust conduit adapted to conduct exhaust gas to an exhaust gas aftertreatment device. The system further includes a low pressure bottom feed fuel injector having an inlet portion fully received within a chamber of an adaptor housing having a lower portion attached to the exhaust conduit. The housing is provided with fuel flow openings to allow low pressure fuel to circulate around and cool the fuel injector inlet portion within the chamber. Fuel injected into the exhaust conduit is preferably targeted toward a vaporization member, within the exhaust conduit, operative to absorb heat from the exhaust gas and vaporize fuel deposited thereon. A plurality of inwardly extending mixing baffles within the exhaust conduit intermediate the vaporization member and the aftertreatment device extend the mixing path to improve fuel vaporization for assisting regeneration of the device.

Description

TECHNICAL FIELD
• This invention relates to regeneration in operation of exhaust gas aftertreatment devices and, more particularly, to an exhaust fuel injection system for initiating such regeneration.
BACKGROUND OF THE INVENTION
• Diesel aftertreatment devices such as catalyzed diesel particulate filters (CDPF) and NO_Xadsorber catalysts (NAC) are known in the art for controlling diesel engine emissions. During diesel engine operation, oxides of nitrogen and carbon particulates are produced as byproducts of combustion. These materials are subsequently collected by the NAC and the CDPF. As the oxides of nitrogen and carbon particulates accumulate within these aftertreatment devices, the aftertreatment devices must be regenerated. This is accomplished by reducing the oxides of nitrogen and oxidizing the carbon particulates held by these devices.
• NAC devices are commonly regenerated by running the diesel engine rich, a few seconds for every minute of engine operation, to provide reducing agents capable of reducing the oxides of nitrogen stored in the NAC. However, as the engine runs rich, fuel may be wasted and the additional fuel may be completely oxidized or generate excess smoke before the reducing agents are used to regenerate the NAC.
• CDPF devices require regeneration at much longer intervals, such as every 200 miles of vehicle operation. Regeneration of a CDPF is usually accomplished by injecting fuel into engine cylinders during their exhaust cycle to form fuel vapors which are carried with exhaust gas for burning in the CDPF. However, depending upon timing and engine operating conditions, the after injected fuel may be completely oxidized or generate smoke before the fuel vapor reaches the CDPF.
• A proposed method of regenerating a CDPF is after-injection, which involves injecting low pressure diesel fuel directly into the exhaust downstream of the engine. However, depending on exhaust gas temperatures, injected fuel may not fully vaporize, resulting in the formation of carbon buildup in the exhaust system.
SUMMARY OF THE INVENTION
• The present invention provides an improved diesel exhaust aftertreatment device regeneration system, which reduces fuel injector temperatures and improves vaporization of after injected fuel during an aftertreatment regeneration event.
• The system includes an exhaust pipe or conduit defining an internal passage for receiving engine exhaust gas and an aftertreatment device, such as a diesel oxidation catalyst (DOC) and a catalyzed diesel particulate filter (CDPF). The exhaust conduit includes an internal fuel vaporization member upstream of the aftertreatment device and a plurality of internal baffles to extend the mixing path and improve fuel vaporization intermediate the vaporization member and the aftertreatment device. The vaporization member is preferably a horizontally extending plate supported within the exhaust conduit by a connecting support. If desired, the plate may have an upturned peripheral rim to temporarily retain unvaporized fuel on the surface of the plate.
• An adaptor housing on the conduit forms a chamber open to the internal passage of the conduit and adapted to conduct fuel through the chamber. A lower portion of the adaptor is attached to the exhaust conduit. A low pressure bottom feed fuel injector, having a fuel inlet sealed within the chamber and a spray nozzle aimed into the internal passage, operates to spray diesel fuel into the internal passage at intervals during engine operation. A pair of fuel flow openings defined by the adaptor housing admit pressurized fuel into the chamber to allow circulation of the fuel around the fuel injector inlet portion. The circulated fuel provides cooling for the fuel injector and the housing to absorb heat transferred from the exhaust gases.
• A fuel pump draws fuel from a fuel supply such as a vehicle fuel tank to supply pressurized fuel to the housing and the inlet portion of the injector.
• An engine control module (ECM), as known in the art, controls fuel delivery through the fuel injector as needed to initiate aftertreatment regeneration.
• During engine operation, exhaust gas flowing through the exhaust gas aftertreatment system first heats the vaporization member and then passes through the DOC to the CDPF, in which carbon particulates are trapped while the cleaned exhaust gas passes through. After a period of time or operating interval in which carbon particulates build up in the CDPF, the ECM activates the fuel injector, causing atomized fuel to spray onto the vaporization member. As the atomized fuel sprayed from the injector makes contact with the heated vaporization member, the fuel is vaporized and mixes with the exhaust gas. As the exhaust gas carries the vaporized fuel through the exhaust conduit toward the aftertreatment device, the baffles extend the mixing path and improve fuel vaporization.
• The vaporized fuel first contacts the DOC, which initiates oxidation of the vaporized fuel. Heat generated by the oxidized fuel travels through the exhaust gas aftertreatment device and oxidizes carbon collected in the CDPF, thereby regenerating the CDPF. After a predetermined period of time, the controller deactivates the fuel injector to terminate the regeneration event.
• These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a diagrammatic view of an exhaust gas aftertreatment system according to the present invention; and
• FIG. 2 is a diagrammatic view of a portion ofFIG. 1 showing the vaporization member and fuel injector mounting together with an associated fuel supply system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
• Referring first toFIG. 1 of the drawings in detail,numeral10 generally indicates a diesel exhaust emission control device regeneration system for regenerating an emission control device in an exhaust system for an internal combustion diesel engine. Thesystem10 includes anexhaust conduit12, defining aninternal passage13, adapted to carry exhaust gas to an exhaustgas aftertreatment device14, such as a diesel oxidation catalyst16 (DOC) mounted ahead of a catalyzed diesel particulate filter18 (CDPF). Theexhaust conduit12 includes an internalfuel vaporization member20 positioned upstream from theaftertreatment device14 and a plurality ofinternal baffles22 intermediate the vaporization member and the aftertreatment device.
• Thevaporization member20 is preferably a horizontally extendingplate24 supported within theexhaust conduit12 by a connectingsupport26. If desired, theplate24 may have an upturnedperipheral rim28 operative to temporarily retain unvaporized fuel on the surface of the plate.
• Anozzle29 of the low pressure bottomfeed fuel injector30 is positioned to direct diesel fuel spray into theexhaust conduit12 onto thevaporization member20, as illustrated inFIG. 2. Aninlet portion31 of thefuel injector30 is mounted in achamber32 of anadaptor housing34 having alower portion36 attached to theconduit12. Thechamber32 is open to theinternal passage13, through anopening37 in the conduit. The housing is provided withfuel flow openings38 and39, which allow fuel flow into and through thechamber32.
• Upper andlower seals40,41 between theinjector30 and thehousing34 prevent leakage of fuel from thechamber32. Thefuel injector30, mounted in thechamber32 operates to receive pressurized diesel fuel from thechamber32 and spray the diesel fuel onto thevaporization member20 in theinternal passage13 of theconduit12 at intervals during engine operation. In addition, pressurized fuel circulating through thechamber32 of the housing provides cooling for the housing and the fuel injector so that its operation is not impaired by hot exhaust gas temperatures.
• Pressurized fuel is preferably supplied from avehicle fuel tank44. A lowpressure fuel pump46 pumps diesel fuel from thefuel tank44 and circulates low pressure fuel in a loop through thehousing32 and back to the fuel tank. Low pressure fuel is continuously circulated through thehousing32 and around thefuel injector30 to cool the fuel injector and the housing. Anoptional heat exchanger48 may be installed intermediate thehousing32 and thefuel tank44 to reduce the temperature of the fuel returned to the fuel tank.
• An engine control module (ECM)50, as known in the art, controls fuel delivery through thefuel injector30 as needed to initiate aftertreatment regeneration.
• During engine operation, exhaust gas is generated during combustion, containing carbon in the form of soot particles. This exhaust gas is subsequently discharged from the engine to theexhaust conduit12. As the exhaust gas flows through theexhaust conduit12, heat from the exhaust gas increases the temperature of thevaporization member20 and thebaffles22. The exhaust gas is further communicated to theaftertreatment device14 where the carbon particulates are collected by the catalyzeddiesel particulate filter18. Over time, carbon buildup in thediesel particulate filter18 could cause increased back pressure to impair the operating efficiency of the engine. To avoid this, periodic regeneration of the particulate filter is required.
• At predetermined intervals or when signaled by a pressure signal, theengine control module50 activates thefuel injector30 to spray fuel onto thevaporization member20. When the fuel contacts with theheated vaporization member20, heat from thevaporization member20 and the surrounding exhaust gases causes the fuel to vaporize and mix with the exhaust gas flowing through theexhaust conduit12.
• When aperipheral rim28 is present around theplate24 of thevaporization member20, the rim aids in retaining unvaporized fuel on the face of the plate to allow additional time for vaporization of the fuel.
• The vaporized fuel and unvaporized droplets are then carried with the exhaust gas through theexhaust conduit12 toward theaftertreatment device14. As the vaporized fuel is carried through theexhaust conduit12 the mixing baffles22 create turbulence, which helps mix the fuel vapor with the exhaust gas. The mixing baffles22 also extend the path between thevaporization member20 and theaftertreatment device14 to allow more time for fuel vaporization.
• When the vaporized fuel and the exhaust gas contact thediesel oxidation catalyst16, the catalyst initiates oxidation of the vaporized fuel, generating heat within theaftertreatment device14. Heat generated by the oxidized fuel, causes oxidation (burning) of the carbon build up in the catalyzeddiesel particulate filter18, thereby regenerating the particulate filter. After a predetermined period of time, theengine control module50, deactivates thefuel injector30 to terminate the regeneration event.
• It should be understood, that theregeneration system10 may be modified and applied to regeneration of other exhaust emission devices, such as a NO_Xadsorber catalyst (NAC). In this instance, the fuel injector may be used in conjunction with the vaporization member and the mixing baffles to provide vaporized fuel between the engine and the NAC to reduce oxides of nitrogen collected by the NAC during engine operation.
• While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.

Claims (14)

1. A diesel exhaust aftertreatment device regeneration system comprising:

an exhaust conduit defining an internal passage connected to carry engine exhaust gas to a downstream aftertreatment device;

an adaptor housing on the conduit and forming a chamber open to the passage, the housing having a lower portion attached to the exhaust conduit and adapted to conduct fuel through the chamber; and

a bottom feed fuel injector having an injection fuel inlet sealed within the chamber and feeding a spray nozzle aimed into the internal passage, the fuel injector positioned to be cooled by recirculating fuel flow through the housing and being operable to spray diesel fuel into the internal passage at intervals during engine operation;

whereby the fuel sprayed into the internal passage is vaporized by hot exhaust gas and carried to the aftertreatment device for assisting regeneration of the device.

2. A system as inclaim 1 including a vaporization member positioned within the exhaust conduit to intercept fuel sprayed into the internal passage, the member being operative to absorb heat from the exhaust gas for vaporizing fuel deposited on the member.

3. A system as inclaim 2 including a plurality of inwardly extending mixing baffles within the exhaust conduit intermediate the vaporization member and the aftertreatment device and operative to extend the internal passage to improve fuel vaporization.

4. A diesel exhaust aftertreatment device regeneration system comprising:

an exhaust conduit adapted to receive engine exhaust gas and connected to carry the exhaust gas downstream to an exhaust gas aftertreatment device;

a vaporization member mounted within the exhaust conduit and operative to absorb heat from the exhaust gas to vaporize fuel deposited thereon; and

a fuel injector operable during engine operation to spray diesel fuel intermittently onto the vaporization member in the exhaust conduit;

whereby fuel injected onto the vaporization member is vaporized by the exhaust heat and is carried to the exhaust gas aftertreatment device for assisting regeneration of the device.

5. A system as inclaim 4 including a plurality of inwardly extending mixing baffles within the exhaust conduit intermediate the vaporization member and the aftertreatment device and operative to extend the mixing path to improve fuel vaporization.

6. A system as inclaim 4 wherein the vaporization member is a plate extending longitudinally within the exhaust conduit and supported within the exhaust conduit by a connecting support.

7. A system as inclaim 6 wherein the plate is generally horizontal and has a raised peripheral rim for temporarily retaining liquid fuel.

8. A system as inclaim 4 including a controller operative to control fuel injection by the fuel injector.

9. A system as inclaim 4 wherein the fuel injector is an electronically controlled bottom feed injector.

10. A system as inclaim 9 wherein the fuel injector has a fuel inlet sealingly received within a housing having a lower portion attached to the exhaust conduit and fuel flow openings to admit pressurized fuel to and allow circulation of the fuel around the injector fuel inlet for cooling the injector.

11. (canceled)

12. A system as inclaim 1 wherein the injection fuel inlet is connected with the spray nozzle for delivering fuel into the internal passage of the exhaust conduit and the adaptor also includes separate fuel openings positioned within the chamber for carrying the recirculating fuel flow through the housing for cooling the injector within the chamber.

13. A diesel exhaust aftertreatment device regeneration system comprising:

an exhaust conduit adapted to receive engine exhaust gas and connected to carry the exhaust gas downstream to an exhaust gas aftertreatment device;

a vaporization member mounted within the exhaust conduit and operative to absorb heat from the exhaust gas to vaporize fuel deposited thereon; and

a fuel injector operable during engine operation to spray diesel fuel intermittently onto the vaporization member in the exhaust conduit;

whereby fuel injected onto the vaporization member is vaporized by the exhaust heat and is carried to the exhaust gas aftertreatment device for assisting regeneration of the device; and

wherein the vaporization member is a plate extending longitudinally within the exhaust conduit and supported within the exhaust conduit by a connecting support and the plate is generally horizontal and has a raised peripheral rim for temporarily retaining liquid fuel.

14. A system as inclaim 6 wherein the plate is generally horizontal.

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